1. Field of the Invention
The present invention relates to a method of evaluating colorectal cancer, a colorectal cancer-evaluating apparatus, a colorectal cancer-evaluating method, a colorectal cancer-evaluating system, a colorectal cancer-evaluating program and recording medium, which utilize the concentration of amino acids in blood (plasma).
2. Description of the Related Art
The number of deaths from colorectal cancer in Japan in 2003 is 21962 males and 18373 females, and the number of deaths from colorectal cancer ranks fourth in males among the deaths from cancers, while the number of deaths from colorectal cancer ranks first in females among the deaths from cancers. The morbidity rate of colorectal cancer in recent years tends to be leveling off.
The five-year survival rate of early colorectal cancer (A and B in Dukes classification) is 80% or higher, and particularly, the five-year survival rate of class A colorectal cancer (tumor remaining within the colorectal wall) is about 90%.
However, the five-year survival rate of progressive colorectal cancer, particularly in class D of Dukes classification (having distal metastasis to the peritoneum, liver, lung and the like) is extremely lowered to about 10%. Therefore, early detection is important for the healing of colorectal cancer.
Here, diagnosis of colorectal cancer includes diagnosis based on the immunological fecal occult blood reaction, diagnosis by colonoscopy, and the like.
However, diagnosis based on a fecal occult blood test does not serve as definitive diagnosis, and most of the persons with positive-finding are false-positive. Furthermore, in regard to early colorectal cancer, there is a concern that both the detection sensitivity and the detection specificity become lower in the diagnosis based on a fecal occult blood test or the diagnosis by colonoscopy. In particular, early cancer in the right side colon is frequently overlooked when diagnosed by a fecal occult blood test. Diagnostic imaging by CT (computer tomography), MRI (magnetic resonance imaging), PET (positron emission computerized-tomography) or the like is not suitable for the diagnosis of colorectal cancer.
On the other hand, colorectal biopsy by colonoscopy serves as definitive diagnosis, but is a highly invasive examination, and implementing colonoscopic examination at the screening stage is not practical. Furthermore, invasive diagnosis such as colonoscopy gives a burden to patients, such as accompanying pain, and there may also be a risk of bleeding upon examination, or the like.
Therefore, from the viewpoints of a physical burden imposed on patients and of cost-benefit performance, it is desirable to narrow down the target range of test subjects with high possibility of onset of colorectal cancer, and to subject those people to treatment. Specifically, it is desirable that test subjects are selected by a less invasive method, the target range of the selected test subjects is narrowed by subjecting the selected test subjects to a colonoscopic examination, and the test subjects who are definitively diagnosed as having colorectal cancer are subjected to treatment.
Incidentally, it is known that the concentrations of amino acids in blood change as a result of onset of cancer. For example, Cynober (“Cynober, L. ed., Metabolic and therapeutic aspects of amino acids in clinical nutrition. 2nd ed., CRC Press.”) has reported that, for example, the amount of consumption increases in cancer cells, for glutamine mainly as an oxidation energy source, for arginine as a precursor of nitrogen oxide and polyamine, and for methionine through the activation of the ability of cancer cells to take in methionine, respectively. Vissers, et al. (“Vissers, Y. L J., et. al., Plasma arginine concentration are reduced in cancer patients: evidence for arginine deficiency?, The American Journal of Clinical Nutrition, 2005. 81, p 1142-1146”) and Park (“Park, K. G., et. al., Arginine metabolism in benign and malignant disease of breast and colon: evidence for possible inhibition of tumor-infiltrating macropharges., Nutrition, 1991. 7, p. 185-188”) have reported that the amino acid composition in plasma in colorectal cancer patients is different from that of healthy individuals.
However, there is a problem that the development of techniques of diagnosing the presence or absence of onset of colorectal cancer with a plurality of amino acids as explanatory variables is not conducted from the viewpoint of time and cost and is not practically used.